This request is a supplement to the 02 year in order to purchase a high speed centrifuge and gradient maker. Data from the first year indicates the lung lamellar body pool to be an excellent index of the surfactant reservoir and an accurate reflection of antecedent synthetic activity. The derivation of the lamallar body fraction from lung homogenate requires the preparation of a discontinuous sucrose density gradient (0.2-0.8 M) and centrifugation at 25,000 rpm x three hours in a Beckman 27.1 rotor. The gradient maker and ultracentrifuge are critical to the expeditious conduct of the influence of hyperoxia and hypoxia on the alveolarization of the rat pup lung.